Abstract

Magnetic fields perpendicular to superconducting films often trigger vortexavalanches, which always are very harmful for electronic devices and other applications. Such avalanches can be suppressed by a metal layer placed in contact with the superconductor surface, an effect that up to now has been thought to be a consequence of improved heat conduction. Here we show experimentally that the role of the metal layer is not that of a heat-sink, but rather that of an electromagnetic drag due to eddy currents induced in the metal layer during the abrupt onset of the flux avalanches. The effect is demonstrated for films of and Nb.

Received 09 February 2010Accepted 10 February 2010Published online 04 March 2010

Acknowledgments:

The authors acknowledge financial support from Brazilian agencies FAPESP and CNPq. Work at Sogang University was supported by MIST/KRF (Grant No. 2009-0051705) of Korea. The work was also supported by the Research Council of Norway.